Glutathione-dependent redox homeostasis is critical for chlorothalonil detoxification in tomato leaves.

Glutathione plays a critical role in plant growth, development and response to stress. It is a major cellular antioxidant and is involved in the detoxification of xenobiotics in many organisms, including plants. However, the role of glutathione-dependent redox homeostasis and associated molecular mechanisms regulating the antioxidant system and pesticide metabolism remains unclear. In this study, endogenous glutathione levels were manipulated by pharmacological treatments with glutathione synthesis inhibitors and oxidized glutathione. The application of oxidized glutathione enriched the cellular oxidation state, reduced the activity and transcript levels of antioxidant enzymes, upregulated the expression level of nitric oxide and Ca2+ related genes and the content, and increased the residue of chlorothalonil in tomato leaves. Further experiments confirmed that glutathione-induced redox homeostasis is critical for the reduction of pesticide residues. RNA sequencing analysis revealed that miRNA156 and miRNA169 that target transcription factor SQUAMOSA-Promoter Binding Proteins (SBP) and NUCLEAR FACTOR Y (NFY) potentially participate in glutathione-mediated pesticide degradation in tomato plants. Our study provides important clues for further dissection of pesticide degradation mechanisms via miRNAs in plants.

Jasmonic acid promotes glutathione assisted degradation of chlorothalonil during tomato growth.

Glutathione (GSH) biosynthesis and regeneration play a significant role in the metabolism of chlorothalonil (CHT) in tomatoes. However, the specific regulatory mechanism of GSH in the degradation of CHT remains uncertain. To address this, we investigate the critical regulatory pathways in the degradation of residual CHT in tomatoes. The results revealed that the detoxification of CHT residue in tomatoes was inhibited by buthionine sulfoximine and oxidized glutathione pretreatment, which increased by 26% and 46.12% compared with control, respectively. Gene silencing of γECS, GS, and GR also compromised the CHT detoxification potential of plants, which could be alleviated by GSH application and decreased the CHT accumulation by 33%, 25%, and 21%, respectively. Notably, it was found that the jasmonic acid (JA) pathway participated in the degradation of CHT regulated by GSH. CHT residues reduced by 28% after application of JA. JA played a role downstream of the glutathione pathway by promoting the degradation of CHT residue in tomatoes via nitric oxide signaling and improving the gene expression of antioxidant and detoxification-related enzymes. This study unveiled a crucial regulatory mechanism of GSH via the JA pathway in CHT degradation in tomatoes and offered new insights for understanding residual pesticide degradation.